1. Field of the Invention
The present invention relates to recording, editing, and reproducing, and more particularly, to a recording medium which stores additional information required in restoring data streams, which are divided by editing/re-recording, to their original state, and a recording method and a restoration method therefor.
2. Description of the Related Art
When data is recorded on a recordable medium, in most cases search data, which is used in decoding, is generated and recorded separately from user data, so that a user can freely edit and reproduce contents. When a user edits/re-records some recorded content, related search data changes in order to reflect details of the edited/recorded-again content.
Conventionally, the search data does not provide a method and/or information for restoring the changed search data to the original state when editing is canceled. Therefore, when information which indicates whether or not an editing function was performed is not recorded, changed search data cannot be restored, particularly in the case of a removable recording medium. This is a problem of the conventional art.
The above relationship between a data stream and search data in a digital versatile disc (DVD) video recorder, to which the above described restoration method is applied, is shown in FIG. 1. FIG. 1 shows a relationship between a data stream, which is recorded on the recording medium, and search data, which is used in managing recorded data streams, which is referred to as Program Cell Information (PGCI). A DVD recorder encodes an input analog image and records the analog image in the form of a digital data stream. Here, one analog image is recorded in the form of a video object (VOB) on the recording medium, and one video object is divided into video object units (VOBUs). A VOBU is a unit for management. A VOBU is data which is recorded from the time when a user begins recording to the time when the user finishes recording, and is recorded in units of a volume of an episode or a movie.
When a user searches for an image in a recording medium in order to replay recorded images, the user searches for data which is recorded in units of programs, because a program is the most widely used unit. When a user records a certain program, the user recognizes the existence of only one program. Internally, however, there exists a cell, which provides meaningful information to users, and video object information (which is referred to as VOBI, VOB Information, or linking information), which actually links cell information (also referred to as search information) to video objects. In the DVD field, cell information or VOBI are called navigation data. Navigation data means data which is used for handling VOBs easily and in various ways, but cannot be seen during actual reproduction.
Cell information includes a lot of information on VOBs, and among it, the starting time of a cell and the ending time of a cell are representative. A cell shown in FIG. 1 includes cell information.
In addition, VOB information includes a lot of information on VOBs, including time MAP (TMAP), which is information on a VOB unit, temporary erase (TE) flag, which indicates whether or not a related VOB is temporarily deleted, the starting time of a VOB, and the ending time of a VOB. For reference, the TMAP in FIG. 2 shows only VOBU playback time (VOBU_PB_TM) among specifications for a DVD video recorder.
In the meantime, an editing function which divides a data stream in a DVD video recorder and restores it later corresponds to temporary deletion. An example of a data stream which is divided by temporary deletion is shown in FIG. 2.
When part of a program is deleted in a DVD video recorder, a cell, VOB information, and a VOB are each divided into two parts. One part is to be temporarily deleted, and the other part is to remain. The TE flag in VOBI for a VOB corresponding to the part to be temporarily deleted is set at “ON” (i.e. changed from TE_OFF to TE_ON). Hatch lined parts indicate temporarily deleted parts. Data in the temporarily deleted parts are not actually deleted, instead, only navigation data are separated from the parts to show deletion effects.
When reproduction is performed, the part without hatch lines, that is 0˜x on the time axis of FIG. 2, is reproduced, and then, after the part with hatch lines is skipped, the part without hatch lines starting from y is reproduced. Here, among VOBs newly generated by temporary deletion, VOBs (VOB1 and VOB3 in FIG. 2) which include partially deleted VOBUs (VOBU1 and VOBU3 in FIG. 2) must be considered. Generally, the starting time of a cell, the ending time of a cell, the starting time of a VOB, and the ending time of a VOB can become different, as shown in FIG. 2, when editing is performed. A cell processes an image in units of a picture, which is shown to a user, while a VOB is processed in units of VOBU, which is a sub-unit of a VOB. An image shown to a user is formed by pictures, each of which is displayed on a screen for {fraction (1/30)} second, or {fraction (1/60)} second, while a VOBU is processed in units of group of picture (GOP) of moving picture experts group (MPEG). In such cases, restoration of a VOB which is temporarily erased causes a problem.
FIG. 3 illustrates an example of restoring a VOB, which is temporarily deleted, using a simple restoration method. In existing DVD video recorders, the simple restoration method in which the TE flag of a VOBI, which is temporarily deleted, is switched from “ON” to “OFF”, is used.
That is, there is a promise in a conventional method that, when a program is temporarily deleted, it is represented by a TE flag. Therefore, when part of a program is temporarily deleted, the existing VOB of the program is divided so that temporarily deleted cells, VOBs, and VOBI are separated from the remaining cells, VOBs and VOBI, and the TE flag in the VOBIs of the temporarily deleted VOBs are set at “ON” in preparation for later restoration. However, since only the TE flag has information on temporary deletion, there is no other way than setting the TE flag to “OFF” when restoring later.
In such a case, as shown in FIG. 2, the second VOB (VOB2) can be restored and reproduced, but temporarily deleted parts included in the first VOB (VOB1) and the third VOB (VOB3), which include partially deleted VOBUs (VOBU1, VOBU3), are not restored. So, it is impossible to restore all data to the way it was before temporary deletion.
Therefore, when the previous simple restoration method is used, the restored program may have two or more cells, VOBs, and VOBI. This means that restoration of temporarily deleted parts after temporary deletion does not result in the original program as shown in FIG. 1. Since restoration after temporary deletion means restoration to the original state from a user's point of view, a method for fully restoring cells, VOBs, and VOBI that are divided by temporary deletion is needed.